In the so-called improved woods, several types of sheet or board materials are available, among which glued laminated wood, including plywood is one of the most popular wood sheet materials.
In general, glued laminated wood which is composed of plural layers of veneers laminated or glued together into a sheet form achieves its thickness from the thicknesses of the individual component veneers and the number of layers of such component veneers. Such glued laminated wood, including plywood, as compared with sawn lumber, exhibits improved uniformity in strength and provides a useful wood sheet material which can be made in much larger areas. Therefore, such glued laminated wood, including plywood comes in a great variety of sizes and thicknesses, and can be laminated in different ways to meet varying requirements of the market. It is therefore used for a wide range of applications including, construction, housing, furniture, etc.
Under present circumstances of limited supply and therefore increasing prices of logs, it is an urgent task of every manufacturer to establish a manufacturing system which can permit production of various kinds of glued laminated wood sheets or panels having different lengths, widths and thicknesses with the highest possible yield rate and the minimum cost in production, labor and materials, in order to fulfill the above-said versatile demands of the market. In addition, it is a potential task of the producer to develop new fields of application for such glued laminated wood through further improvements of its inherent advantages.
It is evident that the above-mentioned urgent problems cannot be solved by glued laminated wood having conventional structure which inevitably calls for and requires selection of component veneers whose sizes are determined by the sizes of the laminated wood sheets or panels to be made. For example, it is presently necessary to cut veneer sheets from a log which is eight feet long in order to make a typical 4'.times.8' plywood panel, for reasons understood by those familiar with the manufacture of plywood. This requirement makes conventional plywood panels more costly. It is therefore believed that an effective approach to the problem would be to establish a technology by which various sizes of glued laminated wood including plywood may be fabricated from veneers of a reduced number of sizes or, most preferably, from veneers of only one size. Moreover, it would be a significant advance if glued laminated wood panels could be manufactured from veneers which are smaller than the intended panel size. In other words, the present invention is intended to provide more effective utilization of veneers. This is because, in the manufacture of glued laminated wood, the process involved in making veneers from logs is more problematic and calls for more labor than does the process of making the laminated wood from the veneers. Thus, improvements in the former process can make a greater contribution to the reduction of costs and to the simplification of laminated wood manufacturing as a whole. However, when realizing a technology which could make possible production of various glued laminated wood sizes from veneers of a reduced number of veneer sizes or of a single size, it would be important to prevent the introduction of any new defects in the products which would be made in that way. The glued laminated wood and the method for its manufacture according to the present invention were developed with these considerations in mind.
Published Japanese Patent Application No. 104006 (1976) shows glued laminated wood composed of a series of short veneers which are all parallel-laminated in such an arrangement that each veneer is offset or shifted with respect to its adjacent veneer at a regular interval of length, and the ends of all of the veneers are exposed on both faces of the sheet. However, the glued laminated wood product of the present invention is different, and is produced in a different way.
It is an object of the present invention to provide glued laminated wood which has improved veneer lamination and is economical to manufacture.
It is another object of the invention to provide glued laminated wood which, when its length and width are given, can be made from veneers whose lengths and/or widths are smaller than those of the laminated wood product to be made.
It is another object of the invention to provide glued laminated wood which can be made longer without being influenced by the given length and/or width of the veneers therefor.
It is still another object of the invention to provide glued laminated wood which can be made in many sizes or dimensions from veneers whose number of sizes or dimensions is reduced.
It is still another object of the invention to provide glued laminated wood which can be made in various forms of veneer lamination.
It is still another object of the invention to provide glued laminated wood which, after forming, is acceptable in appearance and can be used without further processing.
It is another important object of the present invention to provide a method of manufacturing the glued laminated wood product contemplated by the invention.
It is still another object of the invention to provide a continuous method of gluing and laying-up of veneers in making of the glued laminated wood product which has distinct labor saving advantages.